1. Field of the Invention
The present invention relates to an ejector with a throttle controllable nozzle in which two opening degrees of a throat portion and an outlet of the nozzle can be controlled, and an ejector cycle using the ejector. The ejector has a fluid pumping function for circulating a fluid by entrainment of a drive fluid injected at a high speed.
2. Description of Related Art
In an ejector cycle, pressure of refrigerant to be sucked into a compressor is increased by converting expansion energy to pressure energy in an ejector, thereby reducing motive power consumed by the compressor. Further, refrigerant is circulated into an evaporator of the ejector cycle by using a pumping function of the ejector. However, when energy converting efficiency of the ejector, that is, ejector efficiency is reduced, the pressure of refrigerant to be sucked to the compressor cannot be sufficiently increased by the ejector. In this case, the motive power consumed by the compressor cannot be satisfactorily reduced. On the other hand, a throttle degree (passage opening degree) of the nozzle is fixed in the ejector. Therefore, when an amount of refrigerant flowing into the nozzle changes, a nozzle efficiency and the ejector efficiency are changed in accordance with the change of the refrigerant flowing amount. Here, the nozzle efficiency is an energy converting efficiency of the nozzle when the pressure energy is converted to the speed energy in the nozzle.
Further, according to experiments by the inventor of the present invention, if only an opening degree of a throat portion of the nozzle is simply changed, vertical shock wave is generated between a throat portion and an outlet of the nozzle, and the pressure of refrigerant is rapidly changed therebetween. Accordingly, at the outlet of the nozzle, a fluid (refrigerant) is in a subsonic state, and is super-expended. As a result, the refrigerant is not decompressed in iso-entropy in the nozzle, and the nozzle efficiency may be greatly reduced.